Children gain sophisticated reasoning skills, particularly in executive function and working memory, during the adolescent years. Yet, little is known of the neurobiological substrate of these changes. The few studies bearing on this question implicate the maturation of the frontal lobe and its connections. Until recently, it has been difficult to obtain relevant information on frontal lobe maturation in vivo. Postmortem samples have been sparse. Recent advances in magnetic resonance imaging promise to provide increased knowledge of functional and anatomical brain connectivity in vivo. The proposed research exploits these innovations to increase knowledge of frontal lobe connectivity during the adolescent years. Normal adolescents will be studied using novel magnetic resonance imaging techniques within a cross-sectional study. Specifically, developmental changes in functional connectivity will be assessed via analysis of temporal correlations in low-frequency fluctuations of the blood-oxygenated level dependent signal during rest and during a working memory task. Structural connectivity will be evaluated using diffusion tensor imaging and fiber tracking. Substantively, the research aims to establish normal patterns of age-related change in functional and structural connectivity in the working memory network and relate them to pubertal status and hormonal levels. Methodologically, the project seeks to create techniques for measuring functional and structural brain connectivity that can be extended to clinical populations of interest and other cognitive domains. [unreadable] [unreadable]